Natural environmental hazards such as red tides appear to be increasing worldwide. As with other examples of overwhelming natural and man-made environmental risks (e.g. global change), the science surrounding these emerging environmental threats raises more questions than it answers, adding uncertainty to decision making involving these hazards. Currently, very little is known about how people make decisions in situations of uncertain environmental health hazards. Consequently, we do not have the knowledge base needed to devise appropriate educational interventions to facilitate good decision making. The proposed research will address the gaps in knowledge concerning decision making in situations of uncertain environmental health threats, using a theory-based innovative application of conjoint analysis. Specifically, we will explore a) knowledge and awareness of the harmful algal bloom, Florida red tide, and b) factors affecting decisions made about two behaviors in the presence of red tides. Florida red tide is a classic example of a global and emerging environmental hazard with uncertain health risks. Florida red tides may cause health problems when contaminated seafood is eaten and/or when contaminated air is breathed. However, the danger of these consequences is uncertain and the science of red tide hazards is still evolving. Thus, this is an ideal model in which to explore factors affecting decision making in uncertain environmental health situations. For this research, we draw on a conceptual model of decision making using the Precaution Adoption Process Model (PAPM). This model provides a framework that shapes our specific aims, research design and analysis;and informs how we will use study results for future educational activities. The Specific Aims of this research are: Aim 1: Drawing on the PAPM stages theory, we will assess awareness of Florida red tide, knowledge of its consequences, and perceived personal risk from this hazard. Aim 2: Identify the attributes of the choice situations (e.g., physical characteristics, social norms) that are most important to individuals when developing intentions about actions concerning the uncertain environmental health hazards from red tide. Aim 3: Assess where and how individuals receive and prefer to receive information on red tide. The results from this research will be applicable to the wide range of uncertain environmental health hazards facing populations worldwide. Thus, this R21 proposal will serve as the basis of a future R01 application which will: a) disseminate the results of the R21 to harmful algal bloom (HAB) affected coastal communities throughout the Gulf of Mexico;and b) expand and apply the R21 research methodology to decision making about other important environmental health issues (e.g.. sea level rise, microbial pollution) impacting not just our study site of Sarasota FL, but all coastal communities worldwide. PUBLIC HEALTH RELEVANCE: Harmful algal blooms, including Florida red tide, constitute an uncertain environmental health hazard that is growing in magnitude. Decisions that individuals make affect their exposure to potentially negative consequences from these hazards, yet little is known about what affects decision making in these situations. This innovative research will provide information that can be used to facilitate good decision making in the face of these and other environmental health hazards, and thus directly improve public health.